Human Erythrocyte Receptor of l-Fucose-specific Lectin Produced by Streptomyces sp.

L-Fucose-specific lectin produced by Streptomyces no. 16-3 (SFL 16-3) was labeled with N- succinimidyl-2, 3-³H]-propionate to quantitatively investigate its binding to human erythrocytes. The binding inhibition by sugars was competitive, and 5mM L-fucose or 20 mM d-mannose completely inhibited the binding. Among plant lectins, Lotus tetragonolobus, Ulex europeus I, soybean and wheat germ lectin showed competitive inhibition. The association constant and the average number of binding sites for human blood group O erythrocytes were approximately 3 × 10⁷ M^-1 and 1 × 10⁶ cell^-1, respectively. Trypsinization of erythrocytes preferentially increased the number of binding sites for human A and B erythrocytes but not for O erythrocytes.

Membrane components were extracted from human B and O erythrocytes and their binding activity for SFL 16-3 was tested using the hemagglutination-inhibition assay. Poly(glycosyl)-ceramide was the predominant receptor and its fucosyl residue was essential for binding. The crude glycoprotein fraction showed only slight inhibition activity.